The present invention relates to an electromagnetic relay, and more particularly relates to an electromagnetic relay which switches high frequency signals. Generally, in such an electromagnetic relay, excellent high frequency properties and high sealability are required.
Conventionally, in such an electromagnetic relay, to the end of obtaining excellent high frequency properties, it has been proposed to ground a ground terminal which is short circuited to an electroconductive thin film for grounding provided on the base by projecting it from the bottom surface of the base so that the interference between the fixed terminals and the external noises may be removed.
Conventionally, it has been widely practiced to mount a high frequency relay on a printed circuit board on which a certain pattern is formed, but with the increasingly smaller design of high frequency relays there is a tendency that the leakage of high frequency signals is increasing due to the fact that the contact terminals of different poles come closer. Therefore, to the end of obtaining stable and favorable high frequency properties, a high frequency relay is known.
However, problem that arises in particular with an electromagnetic relay for switching high frequency current is that of leakage of high frequency current between the various terminals thereof. It has been practiced to shield the body of the relay, and the mechanisms inside it, as much as practicable, but still the problem is not completely solved. Further, often shielding of the relay terminals is performed by providing a plated surface on the outside body of the relay from which the terminals protrude. When the relay is mounted to, for example, a printed circuit board, and is pressed thereagainst so as to engage the terminals well thereto, then this plated surface is brought into contact with a ground surface on the printed circuit board, and is thereby grounded. However, problems have arisen because, since this plated surface is pressed close against the printed circuit board, it is very difficult to eliminate all residue of flux between them. Such residual flux can cause corrosion, both of the terminals and of the plated surface itself, and this can result in poor electrical contact between the plated surface and the ground surface on the board, which can in turn cause unacceptable high leakage of high frequency current.
Another problem that has arisen with such a plated surface on the relay is that it can occur that poor contact happens between the plated surface and the ground terminals which are providing grounding therefor. This is primarily because the joining area or cross section between such a thin film and a ground terminal protruding from the base is extremely limited in its extent.
Yet another important characteristic for such a relay is good sealability, which has in the prior art proved difficult to obtain as a result of inevitable inaccuracies of manufacture.